1. Field of the Invention
The present invention relates to a display medium, an electrophoretic display, and a method of manufacturing the display medium. The present invention particularly relates to a display medium capable of suppressing irregular coloring to enhance display performance and capable of achieving bright multicolor displays, an electrophoretic display device employing the display medium, and a method of manufacturing the display medium.
2. Description of Related Art
Display media using electrophoresis are well known in the art as a medium for displaying images that can be repeatedly rewritten. However, with these electrophoretic display media, charged particles (particles that migrate in the electrophoretic medium when an electric field is generated) in one pixel can transfer into neighboring pixels, resulting in uneven colors or a drop in contrast. Many of these display media have been provided with partitions between neighboring pixels for preventing the charged particles from transferring from pixel to pixel.
For example, Japanese unexamined patent application publication No. 2003-202601 proposes an image display device having partitions. The partitions are formed by applying a photosensitive paste having a photosensitive resin composition to a substrate, using a photo mask to expose only regions of the paste corresponding to the partitions in order to harden the paste, and subsequently developing and baking the paste.
There are also some display media that are wholly flexible. FIGS. 1(a) and 1(b) illustrate problems that can occur with such a flexible display medium 100 when providing the display medium 100 with solid partitions 140. FIG. 1(a) shows the display medium 100 in an unflexed state, while FIG. 1(b) shows the display medium 100 in a flexed state. The display medium 100 includes a substrate 120, a substrate 130 disposed substantially parallel to the substrate 120, a plurality of line-shaped electrodes 120a and 130a disposed in confrontation with the substrate 120 and substrate 130, respectively, in a simple matrix of orthogonal lines, the solid partitions 140 disposed between the substrate 120 and substrate 130, and an electrophoretic medium (not shown) with dispersed charged particles filling the spaces between the substrate 120 and substrate 130.
When the flexible display medium 100 provided with the solid partitions 140 as described in Japanese unexamined patent application publication No. 2003-202601 is flexed as shown in FIG. 1(b), the partitions 140 are unable to withstand the strain and break or separate at the bonded regions.
To resolve this problem, Japanese unexamined patent application publication No. 2003-15166 describes an electrophoretic display device that seals gaps between the partitions and substrates by providing a soft surface layer on the substrate on which the partitions are not formed and presses the partitions against this surface layer. With the electrophoretic display device disclosed in Japanese unexamined patent application publication No. 2003-15166, the soft surface layer prevents the partitions themselves from being deformed, thereby preventing damage to the partitions.
Electrophoretic display media capable of displaying multicolor images have also been proposed as rewritable display media. Japanese unexamined patent application publication No. 2003-108035 for example discloses a scattering reflection color display body capable of displaying color images by forming color filters in positions corresponding to electrodes disposed on the first substrate above the display medium. Japanese unexamined patent application publication No. 2000-35769 describes another display panel manufactured by injecting three types of nozzles with three different colors of microcapsules and ejecting one capsule at a time from the nozzles onto divided parts of a first electrode using an inkjet system.